1. The Field of the Invention
This invention is in the field of semiconductive device technology. More specifically, this invention is in the field of interposers for electrically connecting semiconductive devices to an electrical apparatus.
2. The Relevant Technology
A semiconductive device is often electrically coupled to an electrical apparatus such as a computer through the use of an interposer. In one such process, the semiconductive device is connected to the interposer, which is then inserted into the socket of the electrical apparatus. The socket may be mounted on the motherboard of a computer, for example. Thus, the semiconductive device communicates electrically through the interposer with the electrical apparatus. Typical interposers currently employed in the coupling of semiconductive devices to electrical apparatuses are comprised of an FR4 fiberglass material, or the like, having electrically conductive metal lines or traces thereon.
The term xe2x80x9csemiconductive devicexe2x80x9d extends to any device or assembly that includes circuitry defined in a semiconductive material, and further extends to a chip package that includes semiconductive material. The external and additional structure of a package assembly may be used, for example, for mounting the semiconductive device to a printed circuit board or other external circuitry, for establishing electrical connection between the semiconductive device and external circuitry, for improving the ease of handling or transporting the semiconductive device, and/or for protecting the semiconductive device from environmental conditions. Many chip packages include a lead frame that extends beyond the body thereof The lead frame typically includes an array of electrical leads that extend from the internal circuitry of the integrated circuit to the exterior portion of the chip package where they are exposed to the surroundings.
Frequently, after a semiconductive device is manufactured, a testing process is conducted on the semiconductive device by subjecting it to a preselected set of input conditions in order to measure its response or other parameters. Testing of an integrated circuit package that includes a lead frame assembly is conventionally conducted by providing temporary electrical communication between the leads and testing circuitry. For example, such temporary electrical connection may be established by using a set of probes, pins, sockets, or the like, to contact the leads. The integrated circuit package may be clamped or otherwise secured in position during the testing operation in order for the leads to remain in electrical contact with the corresponding probes, pins, sockets, etc., of the testing circuitry.
Semiconductive devices, such as DRAMs and SRAMs, undergo significant stresses when in use. Particularly modem, high speed, advanced-integration semiconductive devices generate a significant amount of heat during use. This heat can degrade and slow down semiconductive devices. For example, testing of semiconductive devices to determine the quality and capability of the devices can generate such heat within the devices that the testing process itself damages the devices. Typical fiberglass interposers do not dissipate heat sufficient to protect semiconductive devices from the potential of damage caused by the heat generated during use of the device.
In addition, typical fiberglass interposers are made of glass fibers and epoxy resin. The resulting interposer has a coefficient of thermal expansion which is incompatible with typical semiconductive devices. The coefficient of thermal expansion of the fiberglass is often significantly greater than that of the semiconductive device.
As a result of this thermal expansion incompatibility, shear stresses develop in the interface between the interposer and the semiconductive device when the semiconductive device becomes hot. These shear stresses can result in a severing of the electrical connection between the interposer and the semiconductive device. While it is possible to ameliorate the effects of shearing through a process known as wire bonding, this process adds additional complexity and expense. Furthermore, the organic material within FR4 fiberglass interposers absorbs moisture, causing the interposers to degrade.
There is therefore a need in the art for an improved interposer which assists in protecting a semiconductive device coupled to the interposer from the potential damage caused by significant amounts of heat generated by the semiconductive device. There is also a need in the art for an improved interposer which prevents shear stress from severing the electrical connection between the interposer and the semiconductive device.
An interposer of the present invention is comprised of (i) a substrate comprised of an electrically insulating, thermally conductive ceramic material; and (ii) an electrical conductor on the substrate having a receiving end for connecting to a semiconductive device and a terminal end for connecting to an electrical apparatus. The semiconductive device is electrically coupled to the electrical apparatus when the semiconductive device is connected to the receiving end of the electrical conductor and the terminal end of the electrical conductor is connected to the electrical apparatus. The invention also includes thermally conductive connections between the semiconductive device and an interposer.
In one embodiment, a thermally conductive connector connects the semiconductive device, such as an SRAM, DRAM, or integrated circuit device, to the interposer such that a portion of the semiconductive device is exposed to the atmosphere to thereby dissipate heat to the atmosphere. Both the thermally conductive interposer and the thermally conductive connector act as heat sinks to conduct heat from the semiconductive device to the ambient, thereby protecting the semiconductive device from overheating. The interposer preferably has a coefficient of thermal expansion which is substantially similar to the coefficient of thermal expansion of a semiconductive device on the interposer, thereby preventing shearing of the electrical connection between the semiconductive device and the interposer.
In one embodiment, the semiconductive device is fastened temporarily and removably to the interposer and the interposer is coupled to an electrical apparatus. In another embodiment, the semiconductive device is permanently coupled to the interposer. As an example of a connector, a biasing clip enables quick and convenient placement and removal of semiconductive devices on the interposer. The interposer may be permanently or removably coupled to the electrical apparatus, depending on the desired application.
These and other features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.